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The IDs refer to the different structural variant classes and source call sets, which can also be identified using the SVTYPE and CS tags in the INFO column.
Below is a list of possible SVTYPEs:
ALU: Alu element insertion
LINE1: Line1 transposable element insertion
SVA: SVA element insertion, SVA stands for SINE-VNTR-Alu, it is a composite retrotransposon insertion
INS: Nuclear mitochondrial insertion
DEL: bi-allelic deletion
DUP: bi-allelic duplication
INV: bi-allelic inversion
CNV: multi-allelic copy-number variant
The DEL class has been further re-classified into DEL_ALU, DEL_LINE1 and DEL_SVA if the identified deletion appeared to
correspond to a reference mobile element insertion.
The source call set can be identified using the CS tag in the INFO column. Below is a list of possible CSs:
ALU_umary: Alu element insertion call set from the University of Maryland (MELT algorithm)
L1_umary: Line1 transposable element insertion from the University of Maryland (MELT algorithm)
SVA_umary: SVA element insertion from the University of Maryland (MELT algorithm)
NUMT_umich: Nuclear mitochondrial insertion from the University of Michigan (NumtS algorithm)
DEL_union: Union deletions genotypted by GenomeSTRiP and variant sites identified by GenomeSTRiP, Breakdancer, CNVnator, Delly and Variation Hunter.
DEL_pindel: Small deletions (<1kbp) from Washington University (Pindel algorithm)
INV_delly: Bi-allelic simple inversions from EMBL (Delly algorithm)
CINV_delly: Bi-allelic complex inversions from EMBL (Delly algorithm)
DUP_gs: Bi-allelic duplications and copy-number variants from Broad Institute (GenomeSTRiP algorithm)
DUP_delly: Bi-allelic tandem duplications from EMBL (Delly algorithm)
DUP_uwash: Bi-allelic deletions, duplications and copy-number variants from University of Washington (SSF algorithm)
Further information can be found in the README and the supplementary materials from the phase 3 publication:
I hope this helps but please do get back in touch if you have any further questions.